Biomedical Engineering Reference
In-Depth Information
Fig. 7.2
(
a
) Crystallization
normally takes place via
nucleation, followed by the
growth of crystals. Nucleation
is a kinetic process of
overcoming the nucleation
barrier, which is the outcome
of the occurrence of the
surface free energy
.(
b
)
Illustration of nucleation on a
rough substrate. Reprinted
with permission from Ref.
[
9
], ©2004 Springer
7.3.1
Nucleation Barrier
Nucleation can be regarded as a process of creating “baby crystallites” in the mother
(or ambient) phase. The key step is to overcome a so-called nucleation barrier in the
clustering process, which determines the rate of generating “mature” crystals in the
unit volume of the ambient phase. Under the condition of crystallization, the crystal
phase is the thermodynamically stable phase. As shown in Fig.
7.2
, the occurrence
of nucleation barrier is subject to the occurrence of the interfacial energy between
the crystal phase and the ambient phase. In other words, if there is no interfacial
energy between the ambient and the crystal phases, there will not be any nucleation
barrier.
